Hook up to swss-common logger #45
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| tracing_subscriber::registry() |
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General question: Does this handle Rust's log macros? (info!, warn!, error!, etc.) Would log events go to the tracing subscriber, then into the swsscommon logger infra?
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Yes. swsscommon logger is only used to get log configuration from config_db and reconfigure logger when configuration changed. events do not go through swsscommon logger.
| /// 2. If link_swsscommon_logger is set, use swsscommon logger to get log settings from config_db, which supports dynamic log level change | ||
| /// by modifying config_db. The settings include | ||
| /// - log_level: emerg, alert, crit, error, warn, notice, info, debug | ||
| /// - output: stdout, stderr, syslog. Rust doesn't support dynamically changing log output. We will only support default output (syslog in linux, file in windows) |
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Technically, even though Rust doesn't support having log::set_logger called multiple times, the implementation that's chosen can choose to redirect logs however it chooses to do so. For example, logforth can be used to have a chain of loggers.
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Technically, we can reinitialize tracing system with a new subscriber, but this involves dropping the old subscriber and setting a new one. This will cause a short interruption in logging. Also, I see little use to change log destination. syslog should be sufficient so I didn't implement this.
I am not familiar with logforth. But looking it quickly, it seems not supporting reconfiguring log destination either. See https://docs.rs/logforth/latest/logforth/struct.Builder.html#method.apply
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Ah, I hadn't seen that even logforth doesn't handle reconfiguration.
Why
SONiC uses config_db to keep logger configuration, which allows changing the configuration on the fly. On the back, swss-common logger subscribes to config_db logger table and notifies the corresponding component.
What this PR does
Hook up to swss-common logger to receive configuration update. In response to the change, dynamically changing log level in rust.
This PR can only be committed after sonic-net/sonic-swss-common#969